From the Chief Inspector:
Normally articles about boiler explosions arrive on my desk, but recently an article on an exploding dishwasher arrived, which I thought would interest everybody.

A person was checking vacant housing units and started the dishwasher as part of the inspection. A few minutes later the dishwasher exploded, doing considerable damage to the housing unit.Nobody was hurt in this incident but the potential was there.

At first it was assumed that sewer gas had entered via the drain connection but no evidence of sewer gas could be found in other similar vacant housing units. The dishwasher owner ’s manual provided the answer “…under certain conditions, hydrogen gas may be produced in a hot water system that has not been used for two weeks or more. If the hot-water system has not been used for such a period, before using the dishwasher, turn on all hot-water faucets and let the water flow.”

Tests were carried out on the water lines and extremely high hydrogen readings were found.

Just as operators would not assume that other abandoned piping was safe to work on without checking for explosive contents,even non-flowing hot water lines can be seen to pose a significant hazard potentially.

This article originally appeared in The Pressure News , Volume 6, Issue 3, September 2001